1. Field of the Invention
The present invention relates to an organic electroluminescent display device, and more particularly, to an electromagnetic field preventing and protecting circuit of an organic electroluminescent display device having a separated structure for enabling easy repairing in case abnormal characteristics are generated at an electrostatic preventing circuit for protecting the organic electroluminescent display device from static electricity.
2. Description of Related Art
The organic electroluminescent display device is exposed to electrostatic discharge having high instantaneous voltage by various causes. Since gate insulation film breakage or junction sparking of metal oxide semiconductor (MOS) electric field effect transistor device inside semiconductor device is generated in such cases, the device is completely broken or subtly damaged so that reliability of the device is severely influenced. Therefore, it is considerably important to prevent the gate insulation film breakage or junction sparking in the development stage of the organic electroluminescent display device.
In order to prevent this problem, an electromagnetic field preventing and protecting circuit is used. In the electromagnetic field preventing and protecting circuit, it has been suggested to use a diode ring for preventing damage of internal circuits by connecting a diode between signal lines and power lines.
FIG. 1 is a plan view of an ordinary organic electroluminescent display device.
As illustrated in FIG. 1, an organic electroluminescent display device 100 includes a pixel region 160 having a central part which includes a plurality of unit pixels, such that the pixel region 160 is emitted according to signals applied. The organic electroluminescent display device 100 also includes an upper power supply voltage line 110 wired above the pixel region 160 to apply power supply voltage, and a lower power supply voltage line 130 wired below the pixel region 160 to apply power supply voltage. Further, the organic electroluminescent display device 100 includes a cathode voltage line 120 positioned at one side of the pixel region 160 to apply cathode voltage, a scan driver 140 positioned at the other side of the pixel region 160 to output selection signals, and a data driver 150 formed below the lower power supply voltage line 130 to apply data signals to the pixel region 160.
In the organic electroluminescent display device 100, a power supply voltage is applied to the pixel region 160 from the upper power supply voltage line 110 and the lower power supply voltage line 130, and a cathode voltage is applied to the pixel region 160 from the cathode voltage line 120. When the selection signals and the data signals are applied from the scan driver 140 and data driver 150, respectively, driving circuits formed at unit pixels are switched on so that currents corresponding to the power supply voltage and the data signals are applied to organic EL devices (not illustrated) respectively formed at the unit pixels to display a certain image on the pixel region 160.
As illustrated in FIG. 2, the organic electroluminescent display device 100 includes an electromagnetic field preventing and protecting circuit for controlling characteristics of the electrostatic charges of both sides by discharging the electrostatic charges of one side of the input terminal to the other side of the input terminal when there is something wrong with characteristics of signals applied to respective constituents at an input end of the respective power supply lines 110, 130, for example, if electrostatic charges are generated from one side of the input terminal. Referring back to FIG. 1, a diode ring is coupled between input terminals of the power supply voltage line 110 as shown in circle A.
FIG. 2 is a conventional electromagnetic field preventing and protecting circuit using a diode ring.
An input terminal having sides 170, 170′ is an input terminal of respective power supply lines of the organic electroluminescent display device for receiving input from external devices. A diode ring 180 discharges static electricity transferred through the input terminal 170, 170′, and charge input lines 181, 181′ each have a certain width and transfers static electricity generated from the input terminal 170, 170′ to the diode ring 180, which is formed by diode-connecting a plurality of thin film transistors.
As illustrated in FIG. 2, the charge input lines 181, 181′ are formed, respectively, at an upper side and a lower side of a conventional electromagnetic field preventing and protecting diode ring in such a way that the conventional electromagnetic field preventing and protecting diode ring is connected to the input terminal 170, 170′. The charge input lines 181, 181′ each have a certain width in such a way that the charge input lines 181, 181′ are connected to the input terminal 170, 170′, and the charge input lines 181, 181′ are bent at a certain length of the charge input lines 181, 181′, respectively, so that the bent charge input lines 181, 181′ are connected to the diode ring 180 to transfer static electricity generated from the input terminal 170, 170′ to the diode ring 180.
Charges of one side and the other side of the input terminal are controlled by discharging characteristic signals except for difference of voltage corresponding to the sum total of characteristic signals transmitted through the charge input lines 181, 181′ and the threshold voltages of a plurality of thin film transistors to the other side of the input terminal since the diode ring 180 is formed by diode-connecting a plurality of thin film transistors as illustrated the above. That is, charges of both sides of the input terminal are controlled by transferring the charges from one side of the input terminal having higher charges to the other side of the input terminal having lower charges.
When the conventional electromagnetic field preventing and protecting diode ring is damaged due to high voltage caused by static electricity in the internal structure, the diode ring is separated from the input terminal by applying a laser to the charge input line. However, there is a problem that it takes a long period of time to perform replacement operation of the electromagnetic field preventing and protecting circuit because the width of the charge input line is wider than the diameter of the laser beam so that the application time of the laser beam is lengthened.